Computer Gaming

This I guess could be in geek hobbies as well but since this is going to be a gaming question I will ask it here. I just got a new HP computer last year near christmas but it was only a 600 dollar system because I felt I wasn’t going to do much gaming on it … well I have gotten turned onto Company of Heroes and need to update my graphics card it seems to get any kind of good play out of the game. So how do I figure out whether a new card I pick out won’t hurt the computer and run fine?

edit: It currently has a geforce 6150SE in it so yea i need the upgrade